The present invention relates generally to a torque angle measuring device. More particularly, the present invention relates to a torque angle sensor that measures the degree of torque angle applied beyond a specific point of reference.
The importance of accurately and consistently controlling tension or preload applied to threaded fasteners increases with precision or criticality of parameters and tolerances of the assembly as a whole. This is particularly true in mass production of precision-designed equipment which may later be subjected to maintenance or repair, following which load applied to the assembly fasteners must be substantially the same as that applied during original manufacture. For example, in the manufacture of internal combustion engines designed for high performance and fuel economy, the head is fastened to the engine block with a plurality of bolts prior to final machining of various block/cylinder critical surfaces. In the event that the head is later removed for repair or replacement, it is important that the same be precisely reassembled to the block so as to restore relationships of critical surfaces obtained during the original manufacturing machining operations.
Conventionally, preloading of threaded fasteners in engine and other assembly applications is controlled by monitoring torque applied to the assembly tool, such as with a mechanical or electrical torque wrench. Fastener preload control through monitoring of fastener torque alone, however, yields unpredictable and inconsistent results due in part to varying friction between the mating threads and beneath the fastener head. Where it has been attempted to obtain greater uniformity through use of lubricants or the like, results have continued to be unsatisfactory.
Another approach has been to monitor torque as a function of angle of rotation, determine rate of change of torque, and compare the resulting data during the manufacturing operation to empirically determine data prestored in a computer memory. Such arrangements still do not directly measure fastener tension, and in addition require expensive assembly and control hardware.
A third approach has been to tighten the fastener to a point at which the fastener material yields and the fastener head separates from the threaded body. Arrangements of this type suffer from the same inherent drawbacks as the torque wrench technique described above due to varying friction between the fastener and the assembly, and also increases the cost of both manufacture and repair due to requirement for special double-headed fasteners.
A further technique for controlling fastener preload has been found to yield particularly consistent results. This technique, termed xe2x80x9ctorque-turnxe2x80x9d or xe2x80x9ctorque-angle,xe2x80x9d involves initially tightening the fastener to a specified torque, and thereafter tightening the fastener through an additional prespecified angle. The initial tightening torque is empirically predetermined to be one at which the fastener is tightened in assembly but has not yet been substantially elastically stretched. By thereafter tightening the fastener through an additional angle or fraction of a turn, advantage is taken of the precision machining of the fastener threads so as to obtain predetermined elastic stretching of the fastener within the assembly. For example, a torque-turn or torque-angle fastening specification may call for initial tightening to a torque of twenty-five Newton-meters, followed by an additional one-half turn or a one hundred and eighty-degree rotation in three equal steps.
The following is an example of torque instructions that accompany a service manual and the need for torque angle measurements.
Tighten the cylinder head bolts.
a. Tighten the cylinder head bolts a first pass in sequence to 30 Nxc2x7m (22 lb ft).
b. Tighten the cylinder head bolts a second pass in sequence to 70 degrees.
c. Tighten the cylinder head bolts (1,2,3,4,5,6,7,8) to 70 degrees and the cylinder head bolts (9 and 10) to 60 degrees a final pass in sequence.
Computer-based equipment has been proposed for implementing such fastener preloading technique in mass production operations. However, as previously noted, control during maintenance and repair is as important as control during original assembly.
There remains a need in the art for inexpensive equipment which may be employed by maintenance and repair technicians in the field for obtaining the same precision control of fastener preloading as is done during the original manufacturing operation. Additionally, the products on the market that perform such a function are large and cumbersome. These products use torque angle detection techniques that inhibit their ability as well as for the operability in constrained spaces.
Accordingly, it is desirable to provide a device that is capable of determining the angle of rotation applied to a fastener as well as display the current angle of rotation.
It is therefore an object of the present invention to provide an apparatus that measures the angle of rotation at which a fastener is rotated after a specified torque is applied to the fastener.
It is another aspect of the present invention to provide an apparatus that measures torque angle after a specified torque is applied to a fastener with an apparatus completely sized to function in confining areas.
The above and other aspects are achieved through the use of a novel combination of features as herein disclosed. In accordance with one embodiment of 10 the present invention, a device is used for measuring the angle of torque beyond a specific reference point. The device is comprised of a tool that applies torque to a fastener, an adapter that is attached to the fastener to transfer the torque from the tool, and an apparatus that connects a first end to the tool and a second end to the adapter. The apparatus comprises an angle selector that is adjustable to the desired torque angle, an angle rate sensor that measures the speed and direction of the torque applied, a processor which calculates the current angle from the rate sensor measurements, a zero point indicator that serves as the basis point for the processor to calculate the selected angle, and an angle indicator that alerts as to the torque angle calculated by the processor.
In accordance with another embodiment of the present invention, a device for measuring the angle of torque beyond a specific reference point is comprised of a means for applying torque to a fastener, and a means for measuring the angle of torque as applied to the fastener from a fixed reference point. The means for measuring comprises a means for selecting the desired torque angle, a means for sensing data from the rate and speed of the torque being applied to a fastener, a means for calculating the torque angle from the data, a means for indicating a zero point from which the means for calculating basis its angle torque measurement and a means for indicating the torque angle as determined by the means for calculating.
In accordance with another embodiment of the present invention, a method for determining the torque angle is comprised of selecting the desired angle of torque with an angle selector located on an apparatus. Further steps to the method are indicating the zero point to processor as to the basis point to determine the angle of torque, applying torque to a fastener with a tool to which the apparatus is attached, measuring the rate and speed of the torque with the angle rate sensor starting from the zero point, calculating the area from the rate and speed to arrive at the torque angle, the area is calculated by the processor; and indicating the angle of torque applied through the angle indicator. The apparatus may be comprised of the angle selector, an angle rate sensor, a processor, a zero point indicator and an angle indicator.
In accordance with another embodiment of the present invention, an apparatus is used to determine the torque angle beyond a specific reference point. The apparatus is comprised of an angle selector adjustable to the desired torque angle, an angle rate sensor that measures the speed and direction of the torque applied, a processor which calculates the current angle from the rate sensor measurements, a zero point indicator that instructs the processor as to the basis point to calculate the selected angle, and an angle indicator that alerts as to the torque angle calculated by the processor.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, is for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.